Flexible external cables for use with portable computers are known in the prior art. Examples are shown in U.S. Pat. Nos. 4,417,703, 4,075,420, and 4,812,135. Such cables, intended for use external to the housing of a particular type of electronic device (e.g., a computer) often present unique problems not solved by the prior art. Further, flexible flat cables used in the field of portable electronics, and specifically in the field of portable computers, may present additional problems.
Flexible flat cables are typically fragile. Such cables lack strength due to the relatively small size and flat geometry thereof. Generally, external stress relief devices are required to strengthen the cable but such stress relief members often reduce the flexible properties of the cables.
Flat ribbon-like flexible cables that are unprotected may suffer breakage in bending. Further, stress on flexible cable from pulling the cable may result in tearing and disconnecting of any attached connectors.
When flexible flat cables are employed outside of the protective housing of electronic devices, damage may occur. The exposure of the cables to outside forces may result in accidental piercing and/or cutting of the cable's internal conductive elements. In addition, exposure to industrial environment chemicals may result in corrosive damage.
The desired light weight and small size of flexible flat cables make these ideal for transporting for use with portable computing devices such as laptop and notebook class computers. The trend toward even smaller sub-notebook class computers with less functional hardware increases the need for connection to external devices. Unfortunately the fragile nature of flexible cables inhibit the ability to use them in a traveling environment.
Some attempts to strengthen flexible cables in the prior art, for example U.S. Pat. No. 4,417,703, have included the use of laminated fibers to the ribbon cable. Unfortunately, direct bonding to the ribbon cable changes the electrical characteristics of the cable and, therefore, produces undesirable side-effects.
The length of the cable may also present a problem for travelers. A lengthy cable is often difficult to pack and store. Further, if any substantial length of cable is needed for a networking or communication application, the cable may become entangled and present a potential safety problem.
It is often difficult to predetermine the appropriate length for a cable, so the end user either has to carry a cable that is too long and deal with the disadvantages associated with unneeded cable length. For example, the extra length may be sprawled across the working area. The end user may carry a shorter cable as a remedy for such disadvantages, but there is an inherent risk that the cable will be too short for the job.
Flexible flat cables also tend to be slippery and therefore more difficult to grasp than other cables. This may result in user difficulty in connecting one component to another. Further, the flat geometry yields sharp edges that, in addition to being difficult to handle, present a slight risk of injury.
Flexible flat cables used in portable computing environments may also be susceptible to adverse materials (e.g. chemicals, abrasives, etc.).
Accordingly, a flexible flat cable for use with portable computers and similar devices that overcomes the above described disadvantages is deemed to constitute a significant advancement in the art.